Apple Music and Tidal have leaned on exclusives as the battle to catch up to Spotify's lead in subscribers.

Taylor Martin/CNET

The rivalry between the subscription music giants may be turning bitter.

Spotify has been penalizing some artists who provide music exclusively to its main competitor, Apple Music, according to a Bloomberg report. Citing unnamed people familiar with the practices, the report said Spotify search results bury tunes by artists who give their material to Apple Music first. The company also warned acts it will exclude Apple-exclusive music from featured Spotify playlists once it's available to stream there, the report said.

A spokeswoman for Spotify said statements about burying search results are "unequivocally false." She didn't comment on playlist strategy.

High-profile exclusives have emerged as the weapon of choice for smaller streaming-music services in their battle to catch up with Spotify's lead in subscribers. Unlike Apple Music, Spotify has a free ad-supported tier, which has been a key stepping stone to 39 million paying members. At 15 million users as of June, Apple Music has turned to exclusive material like Frank Ocean's hit "Blonde" in the last week to combat Spotify's advantage on price. Smaller competitor Tidal, owned by rapper Jay Z and a host of other big-name artists, made exclusives its chief selling point.